The objective of this research is to develop a very low cost, in vitro, arterial blood gas (ABG) sensor and associated handheld readout system. ABG measurements are the most frequently ordered tests in intensive care units. The results of Phase I demonstrated excellent accuracy and reproducibility of the optical-based measurements. In addition, optical methods were developed to perform calibration and temperature correction to the data. The multi-analyte sensor was composed of optodes (optical electrodes), one for each analyze of interest, one for calibration and two for temperature sensing. Most importantly, the new, all-plastic biosensor is designed so that it can be mass produced at high speed and low cost. Existing handheld, point of care ABG sensors have not been able to benefit from the very low costs results from totally automated production. As a result, these sensors have had limited success in displacing the service provided by satellite and central laboratories. The new, all-plastic optical sensor is expected to dramatically increase the role of handheld, point of care patient monitoring. The result will be better health care for the patient at lower cost to the hospital. PROPOSED COMMERCIAL APPLICATIONS: The annual market for ABG measurements in the US is in excess of $1B and is at least as much again in the rest of the world. The majority of this market is served by central laboratories. The superior health care provided by existing handheld ABG analyzers do not provide significantly reduced costs. The proposed technology for mass production of low-cost sensors will permit the first serious assault on the hegemony of the central laboratory and provide better health care at lower cost.